Conventionally, an inkjet printer serving as a droplet ejecting device is provided with an inkjet head having nozzles that eject ink droplets onto printing paper for printing an image and the like onto the printing paper. In such an inkjet printer, there arises a problem that ink cannot be ejected from nozzles due to the causes of an increase in viscosity of ink within an ink channel of the inkjet head (hereinafter also referred to as “increased viscosity”), entering of an air bubble into the ink channel, and the like. Hence, a common inkjet printer is configured to perform various maintenance processes, such as a suction purge operation of sucking ink through nozzles and a flushing operation of ejecting ink droplets continuously a plurality of times from the nozzles toward a waste ink receiver prior to or during printing, thereby discharging ink with increased viscosity and an air bubble, together with ink, for recovering the droplet ejection performance of the nozzles.
During the above-described maintenance processes, ink is discharged through the nozzles together with viscosity-increased ink and an air bubble. Thus, if the maintenance processes are performed frequently, the amount of ink discharged vainly increases. Hence, in order to suppress the ink consumption amount during maintenance, a proposed inkjet printer is configured to detect whether nozzles are in a non-ejection state (ejection malfunction) and then to perform a maintenance process only when the non-ejection state is detected in the nozzles.
An inkjet printer disclosed in Japanese Patent Application Publication No. 2006-76311 includes: a serial-type inkjet head (print head) that ejects droplets onto printing paper while moving in a predetermined scanning direction in a reciprocating manner; and a missing-dot detecting section provided at a location outside of a printing region with respect to the scanning direction, the printing region being in confrontation with the printing paper. The missing-dot detecting section includes a light emitting section that emits laser light and a light receiving section that receives the laser light emitted from the light emitting section.
When detecting whether one or more nozzles are in a non-ejection state, a control section of the inkjet printer first controls the inkjet head to move to a region where the light emitting section and the light receiving section of the missing-dot detecting section are arranged, the region being outside of the printing region. Then, the control section controls the nozzles to eject ink droplets in a state where the light emitting section emits laser light toward the light receiving section. At this time, when a droplet is ejected from a nozzle, the ejected droplet blocks part of the laser light. In contrast, when no droplet is ejected from the nozzle, the laser light is not blocked. Accordingly, it is possible to detect whether a droplet is ejected from the nozzle based on a drop amount of light intensity of the laser light received by the light receiving section.